Thermostat control means

ABSTRACT

A thermostat control means is constructed with a pair of stationary contacts engageable by a movable contact upon oppositely directed deflections of a bimetal. A continuously operated cam operates a floating drive member to bodily move the bimetal so that the movable contact cyclically moves toward and away from the stationary contacts. An adjusting cam operating through the drive members is also effective to bodily move the bimetal and movable contact carried thereby. A solid state control circuit is so constructed that momentary engagement of the movable contact with one of the stationary contacts is effective to actuate a relay and maintain such relay actuated until the movable contact momentarily engages the other stationary contact, after which the relay is deactuated and remains deactuated until subsequent momentary engagement of the movable contact with the first of the stationary contacts.

United States Patent Donald J. Bohn 1501 N. Miracle Mile, Tucson, Ariz. 85705 [21] Appl. No. 834,344

[22] Filed June 18, 1969 [45] Patented June 22. 1971 [72] Inventor [54] THERMOSTAT CONTROL MEANS Primary Examiner-Harold Broome Alt0rney-Ostrolenk, Faber, Gerb & Soffen ABSTRACT: A thermostat control means is constructed with a pair of stationary contacts engageable by a movable contact upon oppositely directed deflections of a bimetal. A continuously operated cam operates a floating drive member to bodily move the bimetal so that the movable contact cyclically moves toward and away from the stationary contacts. An adjusting cam operating through the drive members is also effective to bodily move the bimetal and movable contact carried thereby. A solid state control circuit is so constructed that momentary engagement of the movable contact with one of the stationary contacts is effective to actuate a relay and maintain such relay actuated until the movable contact momentarily engages the other stationary contact, after which the relay is deactuated and remains deactuated until subsequent momentary engagement of the movable contact with the first of the stationary contacts.

THERMOSTAT CONTROL MEANS This invention relates to temperature control means for heating and/or cooling systems, and in particular relates to improvements in control means of the type which function by variably modulating the heating and/or cooling source in accordance with temperature difference on a predetermined length cycle basis.

An interior thermostat control unit of the type described in my U.S. Pat. No. 3,050,601 issued Aug. 21, I962 utilizes a synchronous timing motor to drive a cam means which cyclically displaces one contact of a pair of cooperating contacts, with the othercontact of the pair being carried by a bimetal. Whether or not the cooperating contacts engage during a cycle and for what portion of a cycle the cooperating contacts are in engagement is determined by the difference between actual temperature and a desired temperature. It has been found that by utilizing a cycle of predetermined length and variably modulating the application of heat in accordance with the difference between the indicated desired temperature and the existing temperature, the range of temperature fluctuations is maintained within a very narrow band.

In the device of my aforesaid U.S. Pat. No. 3,050,601, as in other prior art devices of that type, snap action between the cooperating contacts is essential and is achieved by utilizing a permanent magnet acting in the contact region.

One such construction, in an arrangement wherein the contacts directly handled load current, utilized a small magnet having its own magnetic circuit separate from the contact, and its air gap adjusted quite small to provide suitable contact pressure when the contacts were together.

Although such type schemes are often referred to as providing true snap action," this is not the case. More particularly, a slowly increasing opening force will cause relay chatter before opening, even with silver alloy contacts. Quite often, this chatter period is of several seconds duration.

The load current" referred to above was usually the energizing current for a relay and was in the order of l ampere at 24 volts and 60 c.p.s. Attempts to eliminate this relay chatter by using only'a few milliamperes on the contacts to actuate a solid state control device were not reasonably satisfactory, due to the same relay chatter problem. Further, the utilization of the magnet for snap action required the use of a relatively stiff bimetal and required large bimetal deflections, both of which are undesirable from production and operating cost viewpoints.

In order to improve overall accuracy of a thermostat control of the type heretofore referred to, the instant invention utilizes a bidirectional controllably conductive solid state power device connected in series circuit with the controlled device for generating heat or cold as required. Another solid state device is part of a circuit utilized to control conduction of the power device. Such circuit requires relatively little current flow to drive the power device into full conduction (low impedance state) or to'drive the power device to cutoff (high impedance state). As will hereinafter be seen, the solid state devices are of a type which are driven into full conduction, and are driven to cutoff, by the momentary application of control signals, and remain either conducting or nonconducting, as the case may be, until the momentary positive application of a control signal of opposite effect.

Because of operation with momentary application of control signals, snap acting bimetal operated contacts are not required, thereby eliminating the necessity for a permanent magnet to operate the contacts. By eliminating the magnet, the necessity for having a long bimetal stroke is eliminated, so that a simple U-shaped bimetal strip may be utilized instead of a coiled bimetal. v

Accordingly, a primary object of the instant invention is to provide novel improved constructions for thermostat control units. 1

Another object is to provide novel control units of this type which may be utilized for both heating and cooling systems.

Still another object is to provide novel control units of this type utilizing controllably conductive solid state devices connected so that only the momentary application of the control signal is required to change conducting states of the devices between cutoff and full ON.

A further object is to provide a novel control unit of this type in which the cyclically operated contact is mounted to the bimetal, which is bodily moved by a drive means and is also bodily movable by an adjusting means.

A still further object is to provide a novel control unit in which there is a continuously operated cam constructed without a sharp dropoff point.

These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings, in which:

FIG. 1 is an electrical and mechanical schematic of a thermostatic control device constructed in accordance with teachings of the instant invention.

FIG. 2 is a simplified electrical diagram of a portion of the circuit shown in FIG. 1.

FIG. 3 is a side elevation of the thermostat unit, including the mechanical elements of FIG. I, with the cover of the unit removed to reveal internal elements.

FIG. 4 is an end view of the unit of FIG. 3, looking in the direction of arrows 4-4 of FIG. 3, with portions of the main support being broken away to reveal internal elements.

Now referring to the Figures, and more particularly to FIGS. I and 2, wherein elements performing like functions have been assigned the same reference numerals. Source 11 supplies 24 volts at 60 cycles which is applied between buses 12 and 13. Operating coil 14, which when energized actuates a heating device [not shown], is connected from bus 13 to main electrode 15 of bidirectional controllably conductive solid state device 18 having its other main electrode 16 connected directly to bus 12. Control electrode 17 is connected to stationary contact 21, positioned on one side of bimetal operated movable contact 20, which is connected through diode 23 to bus 12. Stationary contact 22, on the other side of movable contact 20, is connected through resistor 24 (typically 8,000 ohms) to control electrode 27 of another bidirectional controllably conductive solid state device 28. One main electrode 25 of device 28 is connected through resistor 29 (typically 8,000 ohms) to control electrode 17. The other main electrode 26 of device 28 is connected through diode 31 to bus 13 and is connected through capacitor 32 (typically 5 MP) to main electrode 15.

As will hereinafter become evident, solid state units 18 and 28 areregarded as power and control devices, respectively. Each of the devices 18 and 28 is constructed so that if a very small AC or DC current (approximately 0.002 amperes) is passed through the several hundred ohms from the gate to the main electrode to the left thereof in FIG. 2, a normally nonconducting condition between the respective electrodes immediately reverses and high conduction occurs. If the gate current is discontinued the main circuit instantly becomes nonconductive to AC. However, if DC is used, conduction continues at full rate even when the gate current ceases.

In the circuit of FIG. 2, half-wave DC is impressed at main electrode 26 of device 28, with diode 31 acting as a half-wave rectifier. This half-wave voltage is also impressed on capacitor 32. With the main circuit of device 28 being in its nonconducting state, when contact 20 engages contact 22, gate current is supplied to device 28 so that current flows through resistor 29 to gate 17 of device 18 and through main electrode 16 to bus 12.

This gate current in device I8 sends the main circuit thereof into its conductive state. Because of capacitor 32 the current flowing through resistor 29 and device 18 through gate 17 will be full wave DC. The controlled circuit having been established, the main circuits will continue to conduct even though gate current to device 28 is discontinued. The main current flowing between electrodes 15 and 16 of device 18 flows through relay coil 14 to energize the latter, which in turn operates a heating device (not shown).

To deenergize relay 14, it is necessary to eliminate gate current in device 18. This is done by momentarily operating movable contact into engagement with stationary contact 21, thereby short-circuiting the gate circuit of device 18.

While diode 23 is not required for the ON-OFF functioning of the circuit of FIG. 2, the presence of diode 23 prevents momentary chatter of the relay operated by coil 14, in the event that there is a wrong polarity impressed for a halfcycle.

To return device 18 to its conducting state requires a momentary engagement of movable contact 20 with stationary contact 22.

In prior art temperature control devices of the type under consideration, a single contact was utilized to energize and deenergize the control relay coils; That is, the coil was energized when the contact pair was engaged and was deenergized when the contact pair was disengaged. This required snap-acting contacts which, as will hereinafter be shown, are not required with a device constructed in accordance with teachings of the instant invention.

As seen most clearly in FIGS. 1 and 3, movable contact 20 is mounted to the free end of U-shaped bimetal 40, whose other end is anchored to block 41 secured to the free end of arm 42 which extends generally parallel to the closely spaced arms of bimetal 40. The other end of arm 42 is secured to block 43, which is pivotally mounted to pin 44, projecting forwardly from hollowed support plate 45. From this it is seen that bimetal 40 is part of an assembly which is bodily movable about pin 44 as apivot. As will hereinafter be seen, such movement is achieved through the actions of cams 52 and 55.

Screw 47 extends through a threaded aperture in floating beam 46, the latter being positioned generally parallel to arm 42. The upper end of adjustable pivot screw 47 is rounded, and supports the downward weight of the pivoted thermal strip assembly 40--43 by contacting the bottom surface of arm 42. Lock nut 48, threaded on screw 47, maintains the latter in its adjusted position. Bracket 49 supports guide pin 50 extending upwardly therefrom through aperture 460 in beam 46, The left end of beam 46 rests against the periphery of cam 52, keyed to shaft 53, while the right end of beam 46 rests against the periphery of cam 55, keyed to output shaft 56 of synchronous timing motor 57 positioned to the rear of the surface from which pin 44 projects.

Stationary contact 21 is mounted to bracket 58, and is positioned below contact 20. The lower end of screw 59 threadably mounted to bracket 6] constitutes the other stationary contact 22. Triple pole double-throw switch 63 provides a means for selectively changing electrical connections so that the thermostatic device may be used to control operation of a heating device, through operation of relay coil 14, or a refrigeration device, through the operation of relay coil 99.

With particular reference to FIGS. 3 and 4, it is seen that rotation of knob 54 keyed to shaft 53 is effective to manually position cam 52 to establish a calibration point for manual temperature setting. Motion imparted to beam 46 by positioning cam 52 is transmitted through screw 47, to pivot arm 42 and bimetal 40 connected thereto about pin 44, thereby positioning movable contact 20 with respect to contacts 2], 22. In addition, motion imparted to beam 46 through the continuous rotation of cam 55 is transmitted through screw 47 to arm 42 and bimetal 40 to rock the latter about pin 44.

Because of the novel control circuit of FIG. 2, cam 55 does not require a sharp dropoff point for contact opening, as in similar prior art devices. Further, there is no problem of maintaining firm electrical contact between movable contact 20 and either of the stationary contacts 21, 22. Contact 20 is constructed of relatively light spring material to permit overtravel and overdeflection of bimetal 40. It is noted that when bimetal 40 heats, the arms thereof move toward one another.

Thus, it is seen that the instant invention provides a novel mechanical construction for a thermostat control means, made simple by a novel electronic circuit.

Although there have been described preferred embodiments of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited not by the specific disclosure herein but only by the appending claims.

I claim:

1. Thermostat control means including first and second spaced stationary contacts, a thermostatic element deflectable in opposite directions upon heating and cooling thereof; a third contact operated into engagement with said first contact by said element upon deflection thereof in a first direction; said third contact being operated into engagement with said second contact by said element upon deflection thereof in a second direction; an operating device; a controlled unit operatively connected to said device for control thereby through actuation and deactuation of said device; first and second circuits, each including solid state controllably conductive means for actuating and deactuating said device; momentary engagement of said first and third contacts causing said first circuit to actuate said device and maintain actuation thereof until momentary engagement of said second and third contacts which causes said second circuit to deactuate said device and maintain deactuation thereof until subsequent momentary engagement of said first and third contacts; continuously operable drive means operating said device by bodily moving said element cyclically, thereby moving said third contact cyclically toward and away from said first contact, whereby said third contact engages and disengages said first and said second contacts under predetermined conditions.

2. Thermostat control means as set forth in claim 1, also including adjusting means operable to bodily move said element to a selected position.

3. Thermostat control means as set forth in claim 1, in which the element is a bimetal having one end relatively fixed and the other end movable upon heating and cooling of said element as well as upon operation of said drive means and said adjusting means.

4. Thermostat control means as set forth in claim 3, in which there is a drive member through which motion of both said drive means and said adjusting means are transmitted to said bimetal.

5. Thermostat control means as set forth in claim 4, in which said drive member is an elongated member, one end of which is movable through operation of said drive means and the other end of which is movable through operation of said adjusting means.

6. Thermostat control means as set forth in claim 5, in which there is a pivotal support to which said one end of said bimetal is connected, said drive member extending generally parallel to said bimetal.

7. Thermostat control means as set forth in claim 6, in which there is a projection extending from said drive member and through which motion of said member is transmitted to said bimetal.

8. Thermostat control means as set forth in claim 7, in which said bimetal is elongated and bent into a U-shape; said pivotal support including a pivot and an elongated support member extending generally parallel to the bimetal legs and said drive member; one end of said support member being connected directly to said pivot; the other end of said support member being connected directly to said one end of said bimetal; said projection being in operative engagement with said support member for imparting movement of said drive member to said support member.

9. Thermostat control means including first and second spaced stationary contacts, a thermostatic element deflectable in opposite directions upon heating and cooling thereof; a third contact operated into engagement with said first contact by said element upon deflection thereof in a first direction; said third contact being operated into engagement with said second contact by said element upon deflection thereof in a second direction; an operating device; a controlled unit operatively connected to said device for control thereby through actuation and deactuation of said device; first and second circuits, each including solid state controllably conductive means for actuating and deactuating said device; momentary engagetive means including a control unit and a power unit; said power unit having a main circuit part connected in series with said device; said power unit having a control circuit part connected in circuit with a main circuit part of said control unit. 

1. Thermostat control means including first and second spaced stationary contacts, a thermostatic element deflectable in opposite directions upon heating and cooling thereof; a third contact operated into engagement with said first contact by said element upon deflection thereof in a first direction; said third contact being operated into engagement with said second contact by said element upon deflection thereof in a second direction; an operating device; a controlled unit operatively connected to said device for control thereby through actuation and deactuation of said device; first and second circuits, each including solid state controllably conductive means for actuating and deactuating said device; momentary engagement of said first and third contacts causing said first circuit to actuate said device and maintain actuation thereof until momentary engagement of said second and third contacts which causes said second circuit to deactuate said device and maintain deactuation thereof until subsequent momentary engagement of said first and third contacts; continuously operable drive means operating said device by bodily moving said element cyclically, thereby moving said third contact cyclically toward and away from said first contact, whereby said third contact engages and disengages said first and said second contacts under predetermined conditions.
 2. Thermostat control means as set forth in claim 1, also including adjusting means operable to bodily move said element to a selected position.
 3. Thermostat control means as set forth in claim 1, in which the element is a bimetal having one end relatively fixed and the other end movable upon heating and cooling of said element as well as upon operation of said drive means and said adjusting means.
 4. Thermostat Control means as set forth in claim 3, in which there is a drive member through which motion of both said drive means and said adjusting means are transmitted to said bimetal.
 5. Thermostat control means as set forth in claim 4, in which said drive member is an elongated member, one end of which is movable through operation of said drive means and the other end of which is movable through operation of said adjusting means.
 6. Thermostat control means as set forth in claim 5, in which there is a pivotal support to which said one end of said bimetal is connected, said drive member extending generally parallel to said bimetal.
 7. Thermostat control means as set forth in claim 6, in which there is a projection extending from said drive member and through which motion of said member is transmitted to said bimetal.
 8. Thermostat control means as set forth in claim 7, in which said bimetal is elongated and bent into a U-shape; said pivotal support including a pivot and an elongated support member extending generally parallel to the bimetal legs and said drive member; one end of said support member being connected directly to said pivot; the other end of said support member being connected directly to said one end of said bimetal; said projection being in operative engagement with said support member for imparting movement of said drive member to said support member.
 9. Thermostat control means including first and second spaced stationary contacts, a thermostatic element deflectable in opposite directions upon heating and cooling thereof; a third contact operated into engagement with said first contact by said element upon deflection thereof in a first direction; said third contact being operated into engagement with said second contact by said element upon deflection thereof in a second direction; an operating device; a controlled unit operatively connected to said device for control thereby through actuation and deactuation of said device; first and second circuits, each including solid state controllably conductive means for actuating and deactuating said device; momentary engagement of said first and third contacts causing said first circuit to actuate said device and maintain actuation thereof until momentary engagement of said second and third contacts which causes said second circuit to deactuate said device and maintain deactuation thereof until subsequent momentary engagement of said first and third contacts; said controllably conductive means including a control unit and a power unit; said power unit having a main circuit part connected in series with said device; said power unit having a control circuit part connected in circuit with a main circuit part of said control unit. 